Scripts by Heller and Fili, while teaching nothing about how to draw them, has a really nice selection of images and samples

I agree, it's a lovely book.

It would be nice if there was a contemporary book on the technical side of things though. Notan, rhythm, balance etc.

Have you seen, James Puckett's Type Library? There is a section dedicated to, Lettering & Calligraphy. I am not sure if it is exactly the kind of thing you mean but maybe you could get in touch with him if you are thinking along the same lines? This is the thread he started recently to establish it.